Knowledge of the camber of an ophthalmic lens is important in mounting said ophthalmic lens in an eyeglass frame. This information is used in particular for performing the various steps of such mounting, such as centering the ophthalmic lens relative to the frame, managing the cycles of feeling the ophthalmic lens, drilling or chamfering the ophthalmic lens, measuring the power of said ophthalmic lens and also its prismatic correction (for correcting the prismatic effects of the lens).
It may also be important to verify that the camber of the ophthalmic lens is compatible with the camber of the frame that is to receive it, or to analyze the difference in camber between the left and right ophthalmic lenses of a given pair of eyeglasses.
Finally, on receiving an ordered lens, this information enables the optician to verify that the camber of the received lens does indeed correspond to the desired camber.
At present, the camber of an ophthalmic lens is measured by means of a dedicated appliance known as a spherometer. The principle of such a spherometer is described for example in document U.S. Pat. No. 2,052,153. However that measurement requires rather lengthy manipulation of the ophthalmic lens, thereby increasing the risk of damaging it. In addition, it requires a dedicated appliance to be used. Finally, the use of such a spherometer gives a measurement of the camber that is poorly reproducible since the accuracy of the measured value for the camber depends on how the spherometer is positioned on the ophthalmic lens, and in particular on the transverse inclination of the spherometer relative to the ophthalmic lens during measurement.
There also exist measurement appliances, e.g. appliances for measuring the outline or for centering that also incorporate a spherometer, with one such product being sold under the trademark “Opera Scan” by the supplier Indo. Nevertheless, those measurement appliances are of complex design and require special manipulation of the ophthalmic lens.